GLENWOOD SPRINGS — Garfield County commissioners appeared open Tuesday to a citizen’s proposal to keep water-monitoring wells in place south of Silt as a way to keep track of methane levels and other contaminants in groundwater samples over time.
“I would think that the county has a public health and environmental interest in continuing the well monitoring and to keep that area available for further sampling,” said Lisa Bracken, a West Divide Creek resident who brought to light methane contamination in the creek near her property nine years ago.
Speaking after a public presentation to the county commissioners Tuesday of the Phase III Mamm Creek Area Hydrogeologic Study results by consultants from Tetra Tech, Bracken said she found the results of the study to be “limited, but very useful.”
But, it would be “irresponsible,” she said, to accept the various assumptions and interpretations in the report based on monitoring wells no deeper than 600 feet in the natural gas-rich Wasatch Formation south of Silt without ongoing analysis and review.
Other information, including the conclusions of a 2006 investigation by the Colorado Oil and Gas Conservation Commission into the presence of methane in groundwater that led to new drilling stipulations, is also missing from the study, Bracken said.
The three-phase water quality study supported by the county over the last nine years was intended to help determine the potential impacts of natural gas development on groundwater in the area. It came about after a faulty gas well operated by Encana Oil and Gas was determined to be the source of methane gas that was bubbling up in West Divide Creek in 2004.
The latest report, however, suggests that there is a significant amount of naturally occurring biogenic methane showing up in the shallower test wells that are closer to the typical depth of domestic water wells in the area.
Deeper wells that were tested on four occasions during the study in 2011 and 2012 contained concentrations of what appear to be thermogenic gas, which is the type sought by energy companies and comes from geologic formations deep in the ground, according to the consultants’ report.
It’s unlikely that the thermogenic methane observed in the deeper wells is the source of the shallow biogenic methane, the report concludes.
“The methane concentrations do not specifically point to gas production as the source, and instead is likely naturally occurring,” Chris Gutmann, a hydrogeologist with the consulting firm, concluded in his report to the commissioners Tuesday.
The study “does not show clear evidence of oil and gas impacts on [water quality] in the Wasatch formation,” he said.
The consultants do recommend, however, that the monitoring wells “may be useful to obtain future water-level measurements or water-quality data.”
Commissioners John Martin and Tom Jankovsky suggested it would also be helpful to see if another consultant the county has used in the past for technical analysis, Geoffrey Thyne of Science Based Solutions, would be available to provide a “peer review” of the new study.
“I think it would be appropriate to have him see if there are any issues that may or may not have been overlooked in the study,” Jankovsky said.
Martin concurred that it would be good to “double, triple and quadruple check” the findings.
“The board is kind of in the middle and being pushed in both directions on this,” Martin said in reference to pressures from both the gas industry and environmental interests.
“We want to be fair and have everything out in the open,” he said.
The phase III study also found relatively low concentrations of benzene in the test wells, and in one local domestic well that was included in the study, and is also believed to be naturally occurring.
The first two phases of the Mamm Creek area study were paid for in part using funds from a $371,200 COGCC fine that was levied against Encana as a result of the faulty well that led to the 2004 contamination.
Garfield County paid for the Phase III study.